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427 lsx build need a little help

This is a discussion on 427 lsx build need a little help within the General Help forums, part of the LSx Technical Help Section category; I am currently building a 427 na engine for my 98 t/a and need a little advise. I'm not sure ...

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    midnight blue
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    427 lsx build need a little help

    I am currently building a 427 na engine for my 98 t/a and need a little advise. I'm not sure if the ls6 intake and stock fuel injectors will be enough. I am not too familiar with fuel injection and could use some advise. I will be using the ls1 heads but they are being ported with larger valves at dart right now.I do not have the cam specs but can get them if needed for the advise. Thanks in advance.

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    Veteran Hi-Po's Avatar
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    Who's building the engine?


    Your stock injectors wont cut it and that LS6 intake will severely be hurting that CI engine. These are all things a good reputable engine builder should be going over you honestly.
    Last edited by Spaz; 09-21-2010 at 05:47 AM. Reason: removed non sponsor names

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    midnight blue
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    I'm building the engine. That is why I am asking questions. The car came with the ls6 intake so I wasn't sure if it would be worth putting on the 427. This is the first ls engine and fuel injection venture for me. I used to have a 68 camaro rs with a 406 in it and I have built a few engines but the fuel injection stuff is a little new to me.

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    Welcome to the forum!! Sounds like a cool build there.
    The LS6 intake will work, but it sounds like the FAST 102 might be a better choice for that big cube motor. Stock injectors definitely won't cut it. The cam specs would be helpful for us to know to help you choice injectors size.

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    midnight blue
    1998 Pontiac trans am

    cam specs: Lift is 624 intake and exhaust Lobe centerline 114 intake centerline 111 duration 297 intake and 305 exhaust at.050 247 intake and 255 exhaust Thanks for any help. Also can the opening in the ls6 for the throttle body be opened up to use a 90mm throttle body?

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    Member marksls1ta's Avatar
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    i can get you an intake or injectors for you combo.

    let me know if we can help.

    thanks,
    Mark

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    midnight blue
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    Thanks Mark. I will definately be getting in touch with you on some things. It may be a lttle while as I am buying things as I can afford them.

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    Quote Originally Posted by Kevin Wilson View Post
    I am currently building a 427 na engine for my 98 t/a and need a little advise. I'm not sure if the ls6 intake and stock fuel injectors will be enough. I am not too familiar with fuel injection and could use some advise. I will be using the ls1 heads but they are being ported with larger valves at dart right now.I do not have the cam specs but can get them if needed for the advise. Thanks in advance.
    Like they said, Injectors will not be enough. At this point you can only guess to the best of your knowledge of the HP at the flywheel the engine will make. Don't take this as exact but it can be close. 427 with 241 heads, 90mm Fast, that cam you will use. I'd guess about 650 to the Flywheel.
    To size the injectors this is what you will use

    (Horsepower x B.S.F.C.) / (# of Injectors x Duty Cycle) = Injector Flow
    For Na BSFC will be from .45-.50 Use .50 on the high end.

    So if HP=650 to the Flywheel times the Constant BSFC of .5 divided by the number of injectors times the duty cycle. ( I would Use 80% duty cycle and no higher so that you can have a little room for error.
    So in this case a 50.7 Lb/hr injector would work. This is rated at a fuel rail pressure of 43.5. So in a fuel rail pressure of 58 or so thats in the F-body LS motors this injector woul flow like a 58 lb/hr.
    Hope this helps its always good to have a base before you get started buying parts.

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    midnight blue
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    Thanks Blue, those are answers that are very helpful to me. Has anyone tried the bbk intake or the edelbrock. I really like the fast intake but next year I had plans on putting rectangle port heads on and was going to wait to put a fast intake on then.Thanks again for everyones input.

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    King 0f n00bz shady milkman's Avatar
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    wow..i wish you would have joined earlier and asked before you started spending all this money....with the lsx family ...our top end lags behind our blocks etc..the 427 is a large motor and will have above a 3.9 bore like the base ls1..this means those heads you are using that are designed for a ls1 (shitty heads too compared to everything else out now) will be horrid for your app. you will choking the hell out of your app..basically making it barely better than a ls1....you will NEED a gen IV style head (rectangular port) there are a few..the ls7, ls3 ...the ls3 is one of the cheapest and has good bang for the buck...however for your build i would suggest at least a oem ls7 head...on top of that you will need larger injectors and should be running a ls3,ls7, or fast lsxr 102mm intake manifold...on top of that you will need the throttle body large enough to handle this..a nick williams would be very nice...after that it comes down to a tuning decision ....do you want to run maf or go maf-less and run SD tune..if you go maf..you will need a aftermarket maf ..OEM sensor of course...but for that large of a motor if you could get the tune down a ls7 style card maf would be perfect.

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    i see you are running a 98 ..i would suggest for a build like you are doing ..to upgrade your pcm to a 01+ ..there are writeups on how to do this..imho i would not waste my time with anything you have said so far..the intake, the heads and the stock fuel system.

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    Quote Originally Posted by shady milkman View Post
    i see you are running a 98 ..i would suggest for a build like you are doing ..to upgrade your pcm to a 01+ ..there are writeups on how to do this..imho i would not waste my time with anything you have said so far..the intake, the heads and the stock fuel system.
    I agree, at the very least get yourself some ls3 heads and an ls3 intake. I'm aware that there is more expensive parts out there but the best gain for the money is on the LS3 Heads and Intake. Thats what i'm running on my 416, i just couldnt spend 900 on fast parts when ive compared and raced cars with those parts and still run about the same.

    When I had my LS1 just cammed and aftermarket procomp heads/stock intake/ 3.42 hears. I beat my friend that was running an MS4 cam, ported heads, 4.30 gears. 90 mm BBK intake/BBK throttle body. Volant lid. We went form a 20MPh roll. I still jumped on him and had him by the nose the whole way. Mine was untuned as well. Sometimes spending more money doesn't really help the gain. I'm sure they are proven to flow more but unless you have lots of money, time and a dyno to get the best combo, id say going for the most expensive parts is a hit or miss. IMO if it will be a daily driver not a race car, i wouldn't get the expensive intake. I'd spend that money on expensive rotating parts, forged piston, rods that good stuff.

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    midnight blue
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    When I contacted the guy that does the heads at Dart, who does all of my dads racing heads, he told me he can get the ls1 to flow very well and I told him what I was building. He also said there were better heads but assured me I wouldn't be dissappointed with what I had. I would have loved to have gotten a better set but money is the issue and like I said he told me these would work well, not the best but like I said maybe next year I will purchase the best I can get. I figured I would need to upgrade things like the injectors and such just wasn't sure what I needed. I have a rotating assembly already, it's a manley setup with the bobweight around 1680 so I am at least doing the bottom end as it should be. Already have a converter and tranny. I have to decide on a rear end yet but I need to get the engine done first. I havn't even gotten to drive this car yet because I bought it with a spun rod bearing. I want to get in contact with frost to see which way to go with tune and such because I want to take it to him and have it done. Maybe he can help with some other insight as well like a cpu swap and such.

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    King 0f n00bz shady milkman's Avatar
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    Quote Originally Posted by Kevin Wilson View Post
    When I contacted the guy that does the heads at Dart, who does all of my dads racing heads, he told me he can get the ls1 to flow very well and I told him what I was building. He also said there were better heads but assured me I wouldn't be dissappointed with what I had. I would have loved to have gotten a better set but money is the issue and like I said he told me these would work well, not the best but like I said maybe next year I will purchase the best I can get. I figured I would need to upgrade things like the injectors and such just wasn't sure what I needed. I have a rotating assembly already, it's a manley setup with the bobweight around 1680 so I am at least doing the bottom end as it should be. Already have a converter and tranny. I have to decide on a rear end yet but I need to get the engine done first. I havn't even gotten to drive this car yet because I bought it with a spun rod bearing. I want to get in contact with frost to see which way to go with tune and such because I want to take it to him and have it done. Maybe he can help with some other insight as well like a cpu swap and such.
    i dont want to step on anyones toes here..as your dart guy i am sure knows what he is doing...but gen III heads are a different breed and can be turned into expensive door stops pretty easy...anyone can hog out any gen III head and say it flows well..stock our heads 241s flow well..but there is much more to heads than just flow numbers...velocity being a big one..for a 427 where the stock ls7 heads are the weak link, should tell you to run big cubes..you got to pay to play..

    i understand your financial concerns and complaints but i would not waste your money trying to tune it with those parts as 1. they choke the living shit out of it and 2. it is expensive to tune.

    with that being said..frost is one of the best in the business..i highly suggest you go to him with all of your needs, even more his customer service is off the charts..well worth any price. He tuned my car, and it was a great mail order tune
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    Quote Originally Posted by shady milkman View Post
    i dont want to step on anyones toes here..as your dart guy i am sure knows what he is doing...but gen III heads are a different breed and can be turned into expensive door stops pretty easy...anyone can hog out any gen III head and say it flows well..stock our heads 241s flow well..but there is much more to heads than just flow numbers...velocity being a big one..for a 427 where the stock ls7 heads are the weak link, should tell you to run big cubes..you got to pay to play..

    i understand your financial concerns and complaints but i would not waste your money trying to tune it with those parts as 1. they choke the living shit out of it and 2. it is expensive to tune.

    with that being said..frost is one of the best in the business..i highly suggest you go to him with all of your needs, even more his customer service is off the charts..well worth any price. He tuned my car, and it was a great mail order tune
    If i may ask, what mods did he tune for. I'm sure he's a great tuner, but I don't see a mail order tune being great. It's just my opinion, to me mail order sounds cut and paste like tuning. No two cars are the same much less two motors. Everything comes into play altitude/density, so much changes even two identicle cars at the same altitude. Whats good for one may not be for the other. I agree tuning is expensive, and if you want a tune for your car do it on a dyno. This way you can see how your car reacts to each change. The reason I say this is for compression ratio. Lets say you build and LS1 and change the heads and that changes compression ratio. You tell your tuner you got say...AFR heads, they usually don't ask you what size combustion chamber you got, or what the compression ratio is in your car. If you get a mail order tune with too much timing. Now with that higher comp ratio you will have detonation problems. What if its not enough timing now your car will not perform to its optimum potential. A few degrees of timing eqaul quite a bit of power.

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    Quote Originally Posted by Blue_01_Z28 View Post
    If i may ask, what mods did he tune for. I'm sure he's a great tuner, but I don't see a mail order tune being great. It's just my opinion, to me mail order sounds cut and paste like tuning. No two cars are the same much less two motors. Everything comes into play altitude/density, so much changes even two identicle cars at the same altitude. Whats good for one may not be for the other. I agree tuning is expensive, and if you want a tune for your car do it on a dyno. This way you can see how your car reacts to each change. The reason I say this is for compression ratio. Lets say you build and LS1 and change the heads and that changes compression ratio. You tell your tuner you got say...AFR heads, they usually don't ask you what size combustion chamber you got, or what the compression ratio is in your car. If you get a mail order tune with too much timing. Now with that higher comp ratio you will have detonation problems. What if its not enough timing now your car will not perform to its optimum potential. A few degrees of timing eqaul quite a bit of power.
    mods above in my last post

    mail order tunes are more on the safe side..so it isnt like he is pushing the envelope ..he asks for all your mods and your stats..your h/c/i stats etc ..
    When you have tuned as many cars as frost has..you know what "bolt on" ls1s like..same with mild cams etc..his mail order tunes are not a max effort tune..for h/c/i it is a tune to let it run/idle until you can get a in person tune.

    on the alt. comment...our cars arent like the old carb'd engines..our engines have the map,maf and other sensors to do minor corrects such as elevation and such.. remember from the factory all year cars have the same calibration ..but yet a camaro in denver will not sputter and run like shit ..same as one in new orleans....our pcms are incredibly flexible and smart

    now that i have hp tuners i have been able to compare his mail order tune with the stock..and it is defiantly a large improvement.. not the most i can get out of it ..but a great all around tune...that is why i never hesitate to suggest frost

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    Member Blue_01_Z28's Avatar
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    Thats nice, + on that. I was amazed that my LS3 build with the tune I had Idled and runs pretty good. I monitor my AFR and as long as its not lean only at idle but, thats ok as long as its not under load. I still need to get it tuned on a dyno so I feel better and so I can put that Bottle to USE!!

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    What is the difference between a Maf tune and a speed density tune? I have decided to get the fast intake. Will the 102 throttle body be too much or should it be ok. I'm going to give my heads a shot since I won't have much money in them and some places have told me if they are done right they will be ok. If not I will invest in some other ones. At least I can buy different runners for the fast intake if I decide to change head designs. Anyone know of anyplace that can do a good job on true duel exhaust around the Ohio area?

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    King 0f n00bz shady milkman's Avatar
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    Quote Originally Posted by Kevin Wilson View Post
    What is the difference between a Maf tune and a speed density tune? I have decided to get the fast intake. Will the 102 throttle body be too much or should it be ok. I'm going to give my heads a shot since I won't have much money in them and some places have told me if they are done right they will be ok. If not I will invest in some other ones. At least I can buy different runners for the fast intake if I decide to change head designs. Anyone know of anyplace that can do a good job on true duel exhaust around the Ohio area?
    the 102 is perfect for you. But be warned the 102 fast for ls1,ls2 etc is DIFFERENT than for the ls3-ls7 ....the intake ports wont match up...so if you plan on changing heads (trust me you will..those ls1s will not be able to keep up) you will be going to a 4.00"+ head which are rectangular ports almost exclusively..such as the ls3 heads (i'd recommend these only behind the ls7) then the cathedral port fast 102 will not work !!! so i would choose wisely...the path you are taking now is a expensive one..and will require you to buy a completely new top end.


    the best way to really learn about the plus and negatives of sd vs maf is to go over to ls1 tech and search for "maf vs sd " ..they have a HUGE thread over there with opinions and such from some knowledgeable people.

    Very basic explanation is how the pcm's guess how much air is coming into the engine.

    With the maf..the air passes the hot elements in the maf sensor..as the air crosses the hot elements it response with a hertz value...lets say 2150 for X amount of air ...that info is passed to the pcm and used in conjuncture with the IAT and map and several other sensors and reports and it is referenced to several tables ..such as the spark advance table and such Ve table to tell the pcm how much fuel and advance and a slew of other things should be added or subtracted.

    with a SD you dont use the MAf ...so you rely on MAP and the IAT very heavily and use the VE table for the reference ...
    SD tunes offer very quick throttle performance..not as "laggy" as the maf...also when dialed in..it makes good power.
    MAF tunes allow for a lot more flexibility in terms tuning and outside variables.

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    midnight blue
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    Thanks for the input on the sd vs. maf. I was under the impression I could just purchase the different runners for the fast intake and not replace the whole intake.

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